Staff at the Zealandia Eco-Sanctury have found a bellbird that has the stripe on one side, but the darker male plumage on the other. Also, this bird makes both male- and female- patterened calls, but makes the female calls at a higher volume and greater frequency than is normal for females.
"There's something we can't pin down," says Erin Jeneway, a conservation officer at the sanctuary. "We haven't seen anything like this before."
Although it is the first bellbird to be found with characteristics of both genders, it's not the first such bird or animal to be noted. And there are some species, such as the clownfish, in which members change their sexes. If a female clownfish dies, the largest male in the school will become female.
What do such animals do about their birth certificates?